Database.Persist

Documentation

class PersistField a where

A value which can be marshalled to and from a PersistValue.

Methods

toPersistValue :: a -> PersistValue

fromPersistValue :: PersistValue -> Either String a

sqlType :: a -> SqlType

isNullable :: a -> Bool

Instances

PersistField Bool

PersistField Double

PersistField Int

PersistField Int8

PersistField Int16

PersistField Int32

PersistField Int64

PersistField Word8

PersistField Word16

PersistField Word32

PersistField Word64

PersistField String

PersistField Text

PersistField ByteString

PersistField Html

PersistField TimeOfDay

PersistField UTCTime

PersistField Day

PersistField SomePersistField

PersistField a => PersistField (Maybe a)

class PersistEntity val where

A single database entity. For example, if writing a blog application, a blog entry would be an entry, containing fields such as title and content.

Associated Types

data Key val

The unique identifier associated with this entity. In general, backends also define a type synonym for this, such that "type MyEntityId = Key MyEntity".

data Update val

Fields which can be updated using the update and updateWhere functions.

data Filter val

Filters which are available for select, updateWhere and deleteWhere. Each filter constructor specifies the field being filtered on, the type of comparison applied (equals, not equals, etc) and the argument for the comparison.

data Order val

How you can sort the results of a select.

data Unique val

Unique keys in existence on this entity.

Methods

entityDef :: val -> EntityDef

toPersistFields :: val -> [SomePersistField]

fromPersistValues :: [PersistValue] -> Either String val

halfDefined :: val

toPersistKey :: Int64 -> Key val

fromPersistKey :: Key val -> Int64

showPersistKey :: Key val -> String

persistFilterToFieldName :: Filter val -> String

persistFilterToFilter :: Filter val -> PersistFilter

persistFilterToValue :: Filter val -> Either PersistValue [PersistValue]

persistOrderToFieldName :: Order val -> String

persistOrderToOrder :: Order val -> PersistOrder

persistUpdateToFieldName :: Update val -> String

persistUpdateToValue :: Update val -> PersistValue

persistUniqueToFieldNames :: Unique val -> [String]

persistUniqueToValues :: Unique val -> [PersistValue]

persistUniqueKeys :: val -> [Unique val]

class Monad m => PersistBackend m where

Methods

insert :: PersistEntity val => val -> m (Key val)

Create a new record in the database, returning the newly created identifier.

replace :: PersistEntity val => Key val -> val -> m ()

Replace the record in the database with the given key. Result is undefined if such a record does not exist.

update :: PersistEntity val => Key val -> [Update val] -> m ()

Update individual fields on a specific record.

updateWhere :: PersistEntity val => [Filter val] -> [Update val] -> m ()

Update individual fields on any record matching the given criterion.

delete :: PersistEntity val => Key val -> m ()

Delete a specific record by identifier. Does nothing if record does not exist.

deleteBy :: PersistEntity val => Unique val -> m ()

Delete a specific record by unique key. Does nothing if no record matches.

deleteWhere :: PersistEntity val => [Filter val] -> m ()

Delete all records matching the given criterion.

get :: PersistEntity val => Key val -> m (Maybe val)

Get a record by identifier, if available.

getBy :: PersistEntity val => Unique val -> m (Maybe (Key val, val))

Get a record by unique key, if available. Returns also the identifier.

select

Arguments

:: PersistEntity val

=> [Filter val]

-> [Order val]

-> Int

limit

-> Int

offset

-> Enumerator (Key val, val) m a

Get all records matching the given criterion in the specified order. Returns also the identifiers.

selectKeys :: PersistEntity val => [Filter val] -> Enumerator (Key val) m a

Get the Keys of all records matching the given criterion.

count :: PersistEntity val => [Filter val] -> m Int

The total number of records fulfilling the given criterion.

Instances

MonadCatchIO m => PersistBackend (SqlPersist m)

mkPersist :: [EntityDef] -> Q [Dec]

Create data types and appropriate PersistEntity instances for the given EntityDefs. Works well with the persist quasi-quoter.

persist :: QuasiQuoter

Converts a quasi-quoted syntax into a list of entity definitions, to be used as input to the template haskell generation code (mkPersist).

selectList

Arguments

:: (PersistEntity val, PersistBackend m, Monad m)

=> [Filter val]

-> [Order val]

-> Int

limit

-> Int

offset

-> m [(Key val, val)]

Call select but return the result as a list.

insertBy :: (PersistEntity val, PersistBackend m) => val -> m (Key val, val)

Try to insert the given entity; if another entity exists with the same unique key, return that entity; otherwise, return the newly created entity.

This function is deprecated in favor of insertBy'. In the next major version, this function will be replaced with that one.

insertBy' :: (PersistEntity v, PersistBackend m) => v -> m (Either (Key v, v) (Key v))

This is an improved version of insertBy, indicating whether a new value was inserted. If a duplicate exists in the database, it is returned as Left. Otherwise, the new Key is returned as Right.

checkUnique :: (PersistEntity val, PersistBackend m) => val -> m Bool

Check whether there are any conflicts for unique keys with this entity and existing entities in the database.

Returns True if the entity would be unique, and could thus safely be inserted; returns False on a conflict.